The published record indicates that a multiplicity of fluids is involved in mantle processes leading to the formation of kimberlites and diamonds. It is the purpose of the proposed work to contribute to the clarification of the emerging very complex picture of diamond growth and mantle metasomatism. In particular the PI will attempt to trace the distribution and origin of highly 13C depleted mantle carbon further, following the leeds developed by the work carried out so far. A major new thrust of the proposed work will be the examination of the oxygen isotope record of silicate in inclusions in diamonds and the carbon isotopic composition of the host. The studies will be carried out on suites of samples for which an asthenospheric origin can be postulated as well as on diamonds which were formed at shallower levels. The results of the work will provide an important constraint for hypotheses proposing subduction related origins of diamonds which were formed at 400 to 500 km depth. It is also planned to delineate further the various mantle carbon reservoirs that are presently under discussion, and to establish the joint 813C and 818O record left by mantle metasomatic events.
